Shifted Golgi targeting of glycosyltransferases and α-mannosidase IA from giantin to GM130-GRASP65 results in formation of high mannose N-glycans in aggressive prostate cancer cells

Biochim Biophys Acta Gen Subj. 2017 Nov;1861(11 Pt A):2891-2901. doi: 10.1016/j.bbagen.2017.08.006. Epub 2017 Aug 4.


Background: There is a pressing need for biomarkers that can distinguish indolent from aggressive prostate cancer to prevent over-treatment of patients with indolent tumor.

Methods: Golgi targeting of glycosyltransferases was characterized by confocal microscopy after knockdown of GM130, giantin, or both. N-glycans on a trans-Golgi enzyme β4galactosyltransferase-1 isolated by immunoprecipitation from androgen-sensitive and independent prostate cancer cells were determined by matrix-assisted laser desorption-time of flight-mass spectrometry. In situ proximity ligation assay was employed to determine co-localization of (a) α-mannosidase IA, an enzyme required for processing Man8GlcNAc2 down to Man5GlcNAc2 to enable synthesis of complex-type N-glycans, with giantin, GM130, and GRASP65, and (b) trans-Golgi glycosyltransferases with high mannose N-glycans terminated with α3-mannose.

Results: Defective giantin in androgen-independent prostate cancer cells results in a shift of Golgi targeting of glycosyltransferases and α-mannosidase IA from giantin to GM130-GRASP65. Consequently, trans-Golgi enzymes and cell surface glycoproteins acquire high mannose N-glycans, which are absent in cells with functional giantin. In situ proximity ligation assays of co-localization of α-mannosidase IA with GM130 and GRASP65, and trans-Golgi glycosyltransferases with high mannose N-glycans are negative in androgen-sensitive LNCaP C-33 cells but positive in androgen-independent LNCaP C-81 and DU145 cells, and LNCaP C-33 cells devoid of giantin.

Conclusion: In situ proximity ligation assays of Golgi localization of α-mannosidase IA at giantin versus GM130-GRASP65 site, and absence or presence of N-glycans terminated with α3-mannose on trans-Golgi glycosyltransferases may be useful for distinguishing indolent from aggressive prostate cancer cells.

Keywords: GM130-GRASP65; GNL; Giantin; Golgi α-mannosidase IA; High mannose N-GLYCANS; In situ proximity ligation assay; trans-Golgi glycosyltransferases.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Autoantigens / genetics*
  • Autoantigens / metabolism
  • Biomarkers, Tumor / biosynthesis*
  • Biomarkers, Tumor / chemistry
  • Cell Line, Tumor
  • Glycosyltransferases / chemistry
  • Glycosyltransferases / metabolism
  • Golgi Apparatus / enzymology
  • Golgi Apparatus / metabolism
  • Golgi Apparatus / pathology
  • Golgi Matrix Proteins
  • Humans
  • Male
  • Mannose / metabolism
  • Membrane Glycoproteins / chemistry
  • Membrane Glycoproteins / metabolism
  • Membrane Proteins / antagonists & inhibitors
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism*
  • Polysaccharides / biosynthesis
  • Polysaccharides / chemistry
  • Prostatic Neoplasms / enzymology
  • Prostatic Neoplasms / metabolism*
  • Prostatic Neoplasms / pathology
  • Protein Binding
  • Protein Transport / genetics
  • alpha-Mannosidase / chemistry
  • alpha-Mannosidase / metabolism*


  • Autoantigens
  • Biomarkers, Tumor
  • GORASP1 protein, human
  • Golgi Matrix Proteins
  • Golgin subfamily A member 2
  • Membrane Glycoproteins
  • Membrane Proteins
  • Polysaccharides
  • macrogolgin
  • Glycosyltransferases
  • alpha-Mannosidase
  • Mannose